title: Inclusivity, exclusivity and limit of detection of commercially available real-time PCR assays for the detection of Salmonella.
abstract: The traditional cultural detection of Salmonella spp. is both time- and labour-intensive. Salmonella is often a release criterion for the food industry and time to result is therefore an important factor. Storage of finished products and raw materials can be costly and may adversely impact available shelf-life. The application of real-time PCR for the detection of Salmonella spp. in food samples enables a potential time-saving of up to four days. The advancement of real-time PCR coupled with the development of commercially available systems in different formats has made this technology accessible for laboratories in an industrial environment. Ideally these systems are reliable and rapid as well as easy to use. The current study represents a comparative evaluation of seven commercial real-time PCR systems for the detection of Salmonella. Forty-nine target and twenty-nine non-target strains were included in the study to assess inclusivity and exclusivity. The limit of detection for each of the method was determined in four different food products. All systems evaluated were able to correctly identify the 49 Salmonella strains. Nevertheless, false positive results (Citrobacter spp.) were obtained with four of the seven systems. In milk powder and bouillon powder, the limit of detection was similar for all systems, suggesting a minimal matrix effect with these samples. Conversely, for black tea and cocoa powder some systems were prone to inhibition from matrix components. Up to 100% of the samples were inhibited using the proprietary extracts but inhibition could be reduced considerably by application of a DNA clean-up kit.
authors.affiliation: Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich, CH-8057 Zurich, Switzerland.
authors.forename: H
authors.initials: H
authors.lastname: Margot
authors.forename: R
authors.initials: R
authors.lastname: Stephan
authors.forename: S
authors.initials: S
authors.lastname: Guarino
authors.forename: B
authors.initials: B
authors.lastname: Jagadeesan
authors.forename: D
authors.initials: D
authors.lastname: Chilton
authors.forename: E
authors.initials: E
authors.lastname: O'Mahony
authors.forename: C
authors.initials: C
authors.lastname: Iversen
mesh_terms: D004269:DNA, Bacterial / Q000032:analysis; D005516:Food Microbiology / Q000379:methods*; D057230:Limit of Detection; D060888:Real-Time Polymerase Chain Reaction / Q000592:standards*; D012475:Salmonella / Q000235:genetics*; D012680:Sensitivity and Specificity
chemical_list: D004269:DNA, Bacterial
keywords: Commercial real-time PCR systems; Detection limit; Salmonella detection; Specificity